The present invention is related generally to medical devices. More specifically, the present invention is related to catheters for performing percutaneous myocardial revascularization (PMR) which is also referred to as transmyocardial revascularization (TMR). The present invention includes guide catheters having proximally controllable distally disposed bendable regions.
A number of techniques are available for treating cardiovascular disease such as cardiovascular by-pass surgery, coronary angioplasty, coronary atherectomy, and stent placement. These techniques are generally applied to by-pass or open lesions in coronary vessels to restore patency and increase blood flow to the heart muscle. In some patients, the number of lesions is so great, or the location so remote in the coronary vasculature, that restoring coronary artery blood flow to the heart is difficult. Transmyocardial revascularization (TMR), also known as percutaneous myocardial revascularization (PMR), has been developed as an alternative to these techniques which are directed to bypassing or removing lesions.
Heart muscle may be classified as healthy, hibernating, and xe2x80x9cdead.xe2x80x9d Dead tissue is not dead but is scarred, no longer contracting, and no longer capable of contracting even if adequately supplied with blood. Hibernating tissue is not contracting muscle tissue but is capable of contracting, provided it is again adequately supplied with blood. PMR is performed by wounding the myocardium of the heart, often forming and leaving patent holes, and sometimes injecting angiogenic substances in the process.
PMR was inspired in part by observations that reptilian hearts are supplied in large part by blood supplied directly from within the heart chambers. In contrast, mammalian hearts are supplied by blood pumped from the heart, through the aorta, and back into the heart muscle through the coronary arteries. Positive results have been observed in some patients receiving PMR treatments. The positive results may be due in part to blood being perfused into the myocardium from the heart chambers through holes into the myocardium which remain open. The positive results are believed to be due in part to a wound healing response of the myocardium which includes formation of new blood vessels in the heart wall, which are believed to connect with the heart chamber interior and/or other coronary blood vessels. The PMR procedure can include cutting into the myocardium with therapeutic cutting tips, burning holes with therapeutic tips having laser or radio frequency current burning tips. The PMR therapeutic tip can also be used to inject angiogenic substances, such as growth factors or genes selected to cause angiogenesis.
The PMR procedure generally involves insertion of a therapeutic tip, such as sharp cutting tip, into the heart chamber or chambers selected for treatment. The cutting tip and associated inner shaft can be guided into the chamber through a guide catheter, which may have been inserted into the vasculature a long distance from the heart. After the inner shaft exits the guide catheter, the cutting tip is preferably steered to several positions for forming of several holes in a pattern across the endocardium. In order to steer the inner shaft and cutting tip, an outer shaft or tube is sometimes disposed coaxially about the inner shaft and within the guide catheter. The outer tube can have structural features at the distal end for bending to various angles to reach various locations in the heart wall. The outer tube and inner shaft can be advanced to bring the cutting tip into contact with the heart wall.
It may be desirable to revascularize regions of the endocardium that are difficult to reach using conventional guide catheters. For example, it may be important to reach areas of hibernating tissue in superior locations of the left ventricle. Conventional guide catheters may have difficulty bending sufficiently to reach some regions.
What would be desirable is an improved guide device for steering inner shaft cutting tips into position within the heart myocardium. What would be desirable is a catheter having greater reach and maneuverability in the chambers of the heart.
The present invention includes guide catheters which can be used for performing percutaneous myocardial revascularization (PMR). Guide catheters incorporating the present invention can provide distal regions that can be bent through varying angles. The distal region bending is preferably controlled at a proximal region or proximal end of the guide catheter. One controllably bendable guide catheter has a first lumen for receiving and delivering a therapeutic catheter to the guide catheter distal end and beyond. The guide catheter can also have an elongate manipulation member extending from the proximal region of the guide catheter to near the distal end of the guide catheter. The member is preferably secured to a location off-center from the central longitudinal axis of the catheter. In one embodiment, the distal end of the member is bonded to the body of the guide catheter at the distal end of a second, blind lumen near the guide catheter distal end.
The manipulation member is a pull wire in some embodiments. The manipulation member in one embodiment is a flat metallic ribbon. In some embodiments, the manipulation member is a pull wire which may be formed from metal. In one embodiment, the member is capable of both pushing on the distal region to straighten the distal region and pulling on the distal region through the off-center attachment point to impart a curve or bend to the distal region. In another embodiment, the manipulation member is sufficiently strong only in tension, with a straightening bias in the distal region used to straighten the distal region when tension is released. The guide catheter distal region is preferably formed of a more flexible material than the more proximal intermediate guide catheter region.
A controllably bendable guide catheter, according to the present invention, can be inserted through a conventional guide catheter in one PMR system. In another PMR system, the bendable guide catheter is nested within a second controllably bendable guide catheter. This can provide for great flexibility in reaching otherwise hard to reach sites in the endocardium.
Another aspect of the present invention provides for inhibiting free rotation between nested, rotating tubes such as the nested guide catheter tubes. The rotation inhibitor can include internal and external teeth on opposing external and internal opposing surfaces, respectively. The teeth can engage each other and resist rotation between the inner and outer tubes. When the applied rotational force exceeds a threshold, elastic deformation of the teeth can allow slippage between the opposed teeth and the two tubes. Providing resistance to free rotation between the tubes can lessen the rotation of the two tubes relative to one another in the case where torque has been applied to one tube, but has not been translated to rotational motion at the distal end. The applied torque may have been stored in the intermediate portion of the tube and can cause unwanted rotation of either tube at the proximal end. A ratcheting mechanism can be provided which urges the tubes to stay in position after the treating physician""s hands are removed from the device.